1. Field of the Invention
The present invention relates to a method for controlling a suspension apparatus for a vehicle, and in particular, to an improved method for controlling a suspension apparatus for a vehicle which is capable of significantly enhancing a boarding-on feeling and a driving stability by accurately detecting a road surface condition by using a vehicle sensor.
2. Description of the Conventional Art
As shown in FIG. 1, the conventional electronical control suspension apparatus (ECS) for a vehicle includes a sensor unit for measuring a driving and operational state of a vehicle, an ECU (Central Processing Unit) for computing an operational state using a measured signal, a damper for generating a damping force for controlling the operation of a vehicle, and an electronical type actuator for rotating a control rod of the damper.
In addition, the sensor unit includes a vertical accelerating sensor for detecting an upper and lower direction acceleration, a vehicle speed sensor 2 for computing the speed of a vehicle, a brake on/off sensor 3 for detecting the braking operation, a TPS 4 for detecting a throttle angle of an engine, and a steering sensor 5 for measuring a steering angular speed.
The ECU determines a damping force of the damper based on the signal sensed by the sensor and switches the position of the electronical type actuator 6 disposed above four wheel dampers.
The damper is formed with a multiple type variable damper and an electronical type actuator. The damping force generated by the multiple type variable damper drives the electronical type actuator 6 disposed above the damper and rotates the control rod of the damper, thus varying the side of a flow path and adjusting the damping force of four wheel dampers to a corresponding damping force position.
In the drawings, reference numeral 7 denotes an ECU for electronically controlling elements of the apparatus.
In addition, the conventional ECS system is formed with six logic based on a control state of each element.
First, an anti-bounce control is directed to detecting an operational state of a bumper or the condition of an uneven road. The control is returned to an original state after t1 seconds when the control state is switched to a medium state in a state that the speed of the vehicle is above V1 Kph by detecting the operation state of a bumper or a road condition, and the size of the vertical acceleration of the vehicle positioned at the weight center (console box) of the vehicle is above G1 g.
Second, in an anti-shake control, the control state of the vehicle is switched to a hard state when the speed of the vehicle is below V2 Kph in order to reduce the motion of the vehicle when a passenger gets on or gets off the vehicle when the vehicle is stopping or a predetermined load is loaded onto or unloaded from the vehicle, and is switched to an original state when the speed of the vehicle is maintained at above V21 Kph for t2 seconds.
In the state of a quick sensing operation, namely, when the vehicle runs at a high speed, in order to obtain a driving stability of the vehicle, when the speed of the vehicle is maintained at above V3 Kph for more than t2 seconds, the control state is switched to the medium control state, and when the speed of the vehicle is below V31 Kph, the control state is returned to the original control state.
Third, an anti-squat control is switched to the medium control state when the speed of the vehicle is below V4 Kph and the angle is above .theta.4 degrees of the throttle in order for the front portion of the vehicle to be moved in the upper and lower directions when the vehicle is moved at a low speed.
Fourth, an anti-dive control is switched to a hard mode when a braking switch is turned on by the braking operation when the speed of the vehicle is above V5 Kph in order for the front portion of the vehicle to be minimized in the downward direction when braking the vehicle at intermediate and high speeds.
Fifth, an anti-roll control is switched to a hard control state when the steering angular speeds are more than .theta.61 Deg/sec, .theta.62 Deg/sec, .theta.63 Deg/sec, .theta.64 Deg/sec, respectively, at the time when the speed of the vehicle is V61 Kph, V62 Kph, V63 Kph, V64 Kph, when the speed of the vehicle is above V6 Kph in order to secure the stability of the vehicle when steering the same, and the anti-roll control state is returned to an original state when t6 seconds after the above-described conditions are released.
However, since the above-described conventional ECS system is controlled based on a table made by an input condition of a driver without using the frequency of a road surface and the roughness of the same on which a vehicle runs, it is impossible to obtain a desired boarding-on feeling of a vehicle. Therefore, it is impossible to enhance the boarding-on feeling which is an object of the electronical control suspension apparatus for a vehicle.
In addition, since there are many control factors based on the stability of a vehicle, it is impossible to satisfy all the control factors when they are needed.